Add Item to Playback Queue no longer returns valid JSON and is breaking the client

[dmmulroy]

A change must have been made to the Add Item to Playback Queue api endpoint as it now returns text, just the track id, and this library makes the assumption that all endpoints return valid json. This is causing a SyntaxError to be throw when JSON.parse is called here: https://github.com/spotify/spotify-web-api-ts-sdk/blob/main/src/serialization/DefaultResponseDeserializer.ts#L8

[Mergemat]

same with pausePlayback and startResumePlayback

[DopiGFX]

Can confirm